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In the selection of centrifugal pumps, the type of impeller is a critical factor. Open and closed impellers have distinct characteristics, with significant differences in applicable scenarios. The following comparison from dimensions such as structure, efficiency, and media adaptability helps quickly understand their differences.

I. Structural Differences

• Open Impeller:

Simple in structure, composed of a hub and blades, with the blades directly exposed and no front or rear covers. It resembles a "bare fan blade," allowing fluid to freely enter and exit from both sides of the blades. This design makes it less prone to clogging by impurities, suitable for conveying liquids containing solid particles.

• Closed Impeller:

The blades are wrapped by front and rear covers, forming a closed flow channel, similar to a "fan installed in a box." The covers guide the fluid direction, enhancing energy transfer concentration, but the narrow flow channel is more suitable for conveying clean liquids without solid particles.

II. Efficiency Performance

• Open Impeller:

The efficiency ranges from 50% to 70%. Due to the absence of cover plates fixing the blades, part of the fluid may "leak back" during rotation, causing energy loss. However, its advantage lies in higher tolerance to wear on efficiency—after blade wear, adjusting the gap between the blades and the pump body can still maintain a certain level of efficiency, suitable for long-term use in unstable working conditions.

• Closed Impeller:

The efficiency can reach 70% to 90%. The closed flow channel guides the fluid to flow directionally, reducing energy waste. However, it is sensitive to wear: once the wear rings on the front and rear covers wear out, the fit clearance expands, and efficiency will significantly decline, requiring timely replacement of components.

III. Suitable Media Types

• Open Impeller:

• Recommended Media: Liquids containing solid particles, fibers, or high viscosity, such as sewage, mineral slurry, and syrup.Reason: The open flow channel is not easily blocked, allowing impurities like plastic bags in sewage or small stones in mineral slurry to pass through smoothly.

• Closed Impeller:

• Recommended Media: Clean liquids, such as clear water, oils, and chemical solutions.
• Reason: The closed flow channel requires a "clean environment" to operate efficiently. Once particles enter, they easily get stuck between the blades and covers, leading to pump operation failures.

IV. Maintenance and Cost

• Open Impeller:

• Maintenance: Simple operation—no need to disassemble the entire pump body. The blades can be directly observed, making it easy to clean impurities or inspect wear.
• Cost: Lower manufacturing cost, suitable for scenarios with limited budgets or small-scale equipment. Worn blades can be repaired by cutting or welding, further reducing maintenance costs.

• Closed Impeller:

• Maintenance: Complex process—requires disassembling the pump body to inspect the interior. Especially when wear rings are worn, replacement is time-consuming and labor-intensive.
• Cost: Complex manufacturing process with high initial investment, suitable for large-scale equipment or scenarios requiring high efficiency. However, when operating with clean liquids for a long time, its high efficiency can significantly save energy consumption.

V. Selection Principles: Open or Closed?

Based on the above characteristics, the following principles can be used for quick selection:

• Choose an open impeller: If the medium contains impurities, is highly viscous, or is prone to clogging, or if frequent maintenance is required and the budget is limited.
• Choose a closed impeller: If the medium is clean, high conveying efficiency is required, or the equipment needs long-term stable operation and can accept high initial investment.

We hope this article helps you. If you have product needs, please contact us to discuss your project requirements. Let TEFFIKO help you select the most suitable solution.

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